1. Field of the Invention
This invention relates to methods for predicting the response to HER2-directed therapy in an individual.
2. Background of the Invention
Cellular growth and differentiation processes involve growth factors that exert their actions through specific receptors expressed in the surfaces of responsive cells. Ligands binding to surface receptors, such as those that carry an intrinsic tyrosine kinase activity, trigger a cascade of events that eventually lead to cellular proliferation and differentiation (Carpenter et al., 1979, Biochem., 48: 193-216; Sachs et al., 1987, Cancer Res., 47: 1981-1986). Receptor tyrosine kinases can be classified into several groups on the basis of sequence similarity and distinct features. One of these groups includes the epidermal growth factor receptor family, which includes erbB-1 (also termed EGFR or HER-1) (Carpenter et al., supra); erbB-2 (HER-2/neu) (Semba et al., 1985, Proc. Natl. Acad. Sci., 82: 6497-6501; Coussens et al., 1985, Science, 230: 1130-1139; Bargmann et al., 1986, Cell, Vol. 45, 649-657); erbB-3 (HER-3) (Kraus et al., 1989, Proc. Natl. Acad. Sci., 86: 9193-9197; Carraway et al., 1994, J. Biol. Chem., 269: 14303-14306), and erbB-4 (HER-4) (Plowman et al., 1993, Nature, 366: 473-475; Tzahar et al., 1994, J. Biol. Chem., 269: 25226-25233).
Most tumors of epithelial origin express multiple erbB (HER) receptors and co-express one or more EGF-related ligands suggesting that autocrine-receptor activation plays a role in tumor cellular proliferation. Because these ligands activate different erbB/HER receptors, it is possible that multiple erbB receptor combinations might be active in a tumor, a characteristic that could influence its response to an erbB-targeted therapeutic. ErbB receptors form homodimers and heterodimers that can be stimulated by various ligands leading to downstream signaling events, the extent and nature of which depend on the combination of specific dimers and ligands. For example, HER2/neu appears to be the preferred heterodimerization partner with other members of the epidermal growth factor receptor family, but ultimately the dimers formed are determined by the ligand and the erbB receptors expressed in the cell. Not only may the ligand select the dimerization partners, but it may also influence the time course of membrane translocation, activation, and internalization of the receptor. For example, NDF/Heregulin can stimulate tyrosine phosphorylation of erbB-2 through heterodimerization with either receptors erbB-3 or erbB-4 (Peles et al., 1992, Cell 69, 205-216, Peles et al., 1993, EMBO J. 3, 961-71, Holmes et al., 1992, Science 256, 1205-1210; Tzahar et al., 1994, Biol. Chem., 269, 25226-25233; Plowman et al., 1993, Nature 366, 473-475; Pinkas-Kramarski et al., 1994, Proc. Natl. Acad. Sci. USA, 91, 9387-9391; Pinkas-Kramarski et al., 1996, J. Biol. Chem., 271, 19029-19032; Pinkas-Kramarski et al., 1998, Oncogene, 16, 1249-1258). Depending on the cell line studied, NDF/Heregulin can either elicit a growth arrest and differentiation phenotype, resulting in morphological changes, induction of lipids, and expression of intracellular adhesion molecule-1; or it can induce a mitogenic response (Holmes et al., 1992, Science, 256:1205-1210; Peles et al., 1992, Cell, 69:205-216; Bacus et al., 1993, Cancer Res. 53:5251-5261).
Downstream signaling after ligand binding may be determined by the set of docking proteins that may bind to the activated receptors. For example, activation of erbB receptor heterodimers is coupled to and stimulates downstream MAPK-Erk1/2 and PI3K-AKT growth and survival pathways, whose deregulation in cancer has been linked to disease progression and refractoriness to therapy (Tzahar et al., 1996, Mol. Cell. Biol. 16, 5276-5287; Fukazawa et al., 1996, J. Biol. Chem. 271, 14554-14559, Olayioye et al., 1998, Mol. Cell. Biol. 18, 5042-5051; Lange et al., 1998, J. Biol. Chem. 273, 31308-31316; Hackel et al., 1999, Curr. Opin. Cell Biol. 11, 184-189). HER-3 is a major docking site for phosphoinositide-3-kinase (PI3K). In addition, NDF/Heregulin stimulation causes activation of the PI3K pathway and phosphorylation of AKT (Altiok et al., 1999, J. Bio. Chem. 274, 32274-32278; Liu et al., 1999, Biochem. Biophys. Res. Comm. 261 897-903; Xing et al., 2000, Nature, Med. 6 189-195). These observations implicate PI3K/AKT in the signaling cascade that results from HER-3 heterodimerization with overexpressed HER-2/neu receptors in breast cancer cells; activation of PI3K/AKT promotes cell survival and enhanced tumor aggressiveness (Bacus et al., 2002, Oncogene 21, 3532-3540). In addition, AKT2 was reported to be activated and overexpressed in HER-2/neu-overexpressing breast cancers (Id.).
erbB-2/HER-2 is overexpressed in 20 to 30% of all breast cancers, and its overexpression is associated with poor prognosis, suggesting that it could be used as a target for anti-tumor agents (Slamon et al., 1987; Hudziak et al., 1989; Tagliabue et al., 1991). In erbB-2-overexpressing breast cancer cells, treatment with antibodies specific to HER-2/erbB-2 in combination with chemotherapeutic agents (such as cisplatin, doxorubicin, and taxol) elicits a higher cytotoxic response than treatment with chemotherapy alone (Hancock et al., 1991; Arteaga et al., 1994; Pietras et al., 1994). One possible mechanism by which HER-2/erbB-2 antibodies might enhance cytotoxicity to chemotherapeutic agents is through the modulation of the HER-2/erbB-2 protein expression (Bacus et al., 1992 & 1993; Stancovski et al., 1991; Klapper et al., 1997 & 2000), or by interfering with DNA repair (Arteaga et al., 1994 & 2001; Pietras et al., 1994).
Because of the effect of anti-HER-2/erbB-2 antibodies on cellular growth, a number of approaches have been used to therapeutically target HER-2/erbB-2- or EGFR-overexpres sing cancers. For clinical use, one approach is to interfere with the kinase activity of the receptor by using inhibitors that block the nucleotide binding site of HER-2/neu or EGFR (Bruns et al., 2000; Christensen et al, 2001, Erlichman et al., 2001, Herbst et al., 2002; Hidalgo et al, 2001; Moasser et al, 2001; Fujimura et al., 2002; Normanno et al., 2002). A second approach is using ansamycins to influence the stability of HER2/neu receptors (Munster et al., 2002; Basso et al, 2002). Another approach is the use of antibodies directed to various erbB receptors, specifically EGFR or HER-2/neu (Alaoui-Jamali et al., 1997; Albanell et al., 2001(a); Baselga et al., 1994 & 2002; Mendelsohn, 1990). Analysis of various antibodies to HER-2/neu led to the identification of the murine monoclonal, 4D5. This antibody recognizes an extracellular epitope (amino acids 529 to 627) in the cysteine-rich II domain that resides very close to the transmembrane region. Treatment of breast cancer cells with 4D5 partially blocks NDF/heregulin activation of HER-2-HER-3 complexes, as measured by receptor phosphorylation assays. To allow for chronic human administration, murine 4D5 was fully humanized to generate trastuzumab/HERCEPTIN® (Sliwkowski et al., 1999; Ye et al., 1999; Carter et al, 1992; Fujimoto-Ouchi et al, 2002; Vogel, et al., 2001 & 2002).
A number of monoclonal antibodies and small molecule, tyrosine kinase inhibitors targeting EGFR or erbB-2 have been developed. For example, HERCEPTIN® is approved for treating the 25% of women whose breast cancers overexpress erbB-2 protein or demonstrate erbB-2 gene amplification (Cobleigh et al., 1999, J. Clin. Oncol. 17, 2639-2648). In addition, several EGFR-targeted therapies are currently under clinical investigation (Mendelsohn & Baselga, 2000, Oncogene 19, 6550-6565; Xia et al., 2002, Oncogene 21, 6255-6263).
The development of successful oncological drugs has followed a well-established evaluation process including phases I, II, and III clinical trial. Phase I studies aim to determine the maximally tolerated dose of the drug, its optimal schedule of administration and the dose-limiting toxicities. Historically, cytotoxic cancer therapies have been developed based on maximum tolerated doses (MTD), treating patients without understanding the tumor profile for likely responders. Hence, patients were often subjected to toxic therapies with limited therapeutic benefit. Recently, elucidating tumor growth and survival pathways has led to the development of tumor-targeted therapies. For such targeted therapeutics that are not expected to produce serious adverse side effects, relying on a MTD may not be suitable. More relevant may be the determination of the optimal dose and schedule that is sufficient to inhibit cellular signaling in patient samples. Biological assays for signaling biomarkers are needed to establish such a protocol.
Preclinically, most erbB-receptor targeted therapies primarily exert cytostatic anti-tumor effects, necessitating their chronic administration in clinical practice. Identification of biologically effective doses (BED), the dose or dose range that maximally inhibits the intended target, beyond which dose escalation is likely to add toxicity without benefit, is therefore essential. Moreover, many of these agents will be used in combination with cytotoxic therapies, where added toxicity may not be tolerable, further supporting BED-based dosing. “Targeted-therapy” implies that populations of likely responders exists, and can be identified.
In view of the severe and deleterious consequences of administering an inappropriate or ineffective therapy to a human cancer patient, there exists a need in the art for predicting the response to cancer therapy in an individual. Further, there is a need to develop diagnostics that are capable of predicting patient response for the successful development and clinical acceptance of new HER-2 targeted therapeutics similar to HERCEPTIN®.